Field of the Invention
This invention relates to a tablet having an optical security feature formed as a diffractive micro-structure, a compression die for producing such tablets and a method for producing such tablets.
Discussion of Related Art
Counterfeit and gray market products and illegal re-imports are a major problem for pharmaceutical drugs. Drugs and medicines are counterfeited to an ever increasing extent, which is a problem not only in developing countries, where counterfeit products in the supply chain often amount to more than 50%, but this problem also exists in industrial countries where the prices of pharmaceutical drugs are often much higher. The prices for AIDS drugs or cancer drugs are often reduced significantly in developing countries, for example, for social reasons, but this increases the risk of abusive re-importing of these drugs into industrial nations.
To prevent abuse, packages of pharmaceutical drugs are provided with counterfeit-proof features. Holograms, optically variable inks, fluorescent dyes, special printing techniques such as microprinting and other security features are attached to the package with adhesive labels, are laminated onto the box or are applied directly to the package. One main disadvantage of such labeling is that it can be removed from the product or package and then reused or analyzed. Some companies apply security features to the sealing film of blister packs, but these have the same disadvantages.
Methods of applying counterfeit-proof signatures, such as DNA of a known sequence, U.S. Pat. No. 5,451,505, for example, molecules with a characteristic isotope composition or microparticles with a characteristic color layer sequence, U.S. Pat. No. 6,455,157, for example, are extremely critical because these signatures are taken together with the drug. For this reason, approval authorities such as the U.S. Food and Drug Administration (FDA) have not yet given approval for such methods.
Some attempts to apply a hologram to edible products have been published. PCT International Publication WO 01/10464 A1 discloses the coating of edible products with a thermally moldable and embossable layer. However, the application of this layer alters the composition and the production process of pharmaceutical pills, so it requires a new official approval. In addition, heating during the thermal shaping steps is problematical for many active ingredients.
U.S. Pat. No. 4,668,523 describes another approach in which a polymer solution is brought in contact with a mold having a diffractive relief. Then the polymer is hardened by drying. This step can be accelerated by heating. At the end, the hardened, edible polymer product carries the diffractive relief. This method is limited to polymer solutions and is very slow. In addition, the heating of the active ingredients used for the production of pharmaceutical tablets is again problematical. These disadvantages have prevented the market introduction of these techniques.